Carbohydrate Sweeteners

May 2005

Carbohydrate Sweeteners

By Elaine KnehrContributing Editor

Carbon, hydrogen and oxygen are generally studied in chemistry, not food science. Together they form carbohydrates, important compounds that contribute texture, flavor and structure to foods. These sugars, starches, pectins, celluloses and certain gums have a long and valuable history of use in prepared foods.

Sugars, in particular, are highly versatile -- useful in small amounts, such as to round-out a flavor, or as the primary ingredient in a confectionery. Over the years, high-intensity, nonnutritive sweeteners were developed. While they have an important place in the market, carbohydrate nutritive sweeteners provide the gold standards in taste and functionality across the food spectrum.

A spoonful of sugar Nutritive sweeteners provide calories. Sucrose, a disaccharide of the monosaccharides glucose and fructose, has historically been the sweetener of choice. Not simply valued for its pleasant, sweet taste, sugar contributes important functionalities, such as browning and fermentation regulation in baked goods, bulk and rich texture in ice cream and jams, viscosity in beverages, and flavor enhancement in sweet and savory products. Sucrose has good solubility, controls crystallization and can improve shelf life.

Sugar is available in numerous forms. Dry, white cane products include powdered, multipurpose granulated and extra-large crystals (useful for slow dissolution). Liquid cane sugars, typically 67?Brix, offer easy storage and handling and provide mouthfeel in soft drinks, creamy tones to dairy desserts and balanced flavor in sauces and vinegar-based products. Processors prepare brown cane sugars by coating sucrose crystals with molasses. The products range from light brown to dark brown and possess distinctive color and flavor intensities, which contribute characteristic "golden" profiles to toffees and caramels, and "wholesome" notes to muffins and cereal bars. Turbinado sugar, washed, raw sugar with a light-tan color and molasses-type flavor, is often used in natural-type products.

An earful about sweeteners Corn-derived sweeteners are extensively used as economical sources of sweetness and functionality. "The different corn-sweetener products are composed of various combinations of individual sugars, which determines ingredient functionalities," explains Sharon Walbert, director of technical services, Cargill Sweeteners, Naperville, IL. "Liquid, nutritive corn sweeteners may be broadly categorized as high-fructose corn syrups and glucose syrups, which include high-glucose (or dextrose) and high-maltose syrups, and a wide range of multiuse corn syrups."

High-fructose corn syrup (HFCS) is prepared by the hydrolysis of corn starch into glucose, followed by the isomerization of glucose into its fructose isomer. Blending the glucose and fructose streams achieves the desired sugar ratio. Standard products contain 42%, 55% and 90% fructose with, for example, 42% HFCS having a sweetness equivalent to sucrose.

The composition of corn sweeteners affects their relative sweetness level. "The type of saccharide or sugar the sweetener is composed of will determine its sweetness," says Michelle Kozora, food scientist, technical services, Tate & Lyle, Decatur, IL. "Sugar has a relative sweetness of 100. By comparison, fructose has a relative sweetness of 117 and dextrose has a relative sweetness of 67. The higher the level of fructose in a corn sweetener, the sweeter it will be. So, a corn sweetener like Tate & Lyle's NETO® 7350, which is a high-maltose syrup composed of mostly dextrose and maltose, will not be as sweet as our ISOSWEET® 100 product, which is a 42% high-fructose corn syrup composed of mostly dextrose and fructose."

The industry typically uses one of two HFCS products. "The 42%-fructose product has a relative sweetness of 92, and the 55%-fructose product has a relative sweetness of 99 -- on a same-solids basis," explains Kozora. "So, HFCS has nearly the same sweetness as sugar. Other common corn syrups include the regular conversion corn syrups, which have a lower relative sweetness near 30, and high-maltose corn syrups, which have a relative sweetness around 34. So, basic corn sweeteners are used mostly to provide body and bulk, whereas the HFCS or fructose products provide body as well as sweetness."

Functionally, HFCS is a good humectant, controls crystallization, supplies a yeast-fermentable substrate, has a low viscosity and blends readily with acids, flavorings and other sweeteners. "These syrups have widespread functional uses, including the ability to supply sweetness in beverages, develop sheen and balance the acidity in catsup, and extend the shelf life of baked goods by retaining moisture," notes Walbert.

Less sweet than sucrose, corn syrup contributes body to ice cream and reduced-fat products like salad dressings and dairy desserts, and is used in confections to control crystallization, slow the dissolving rate in the mouth and provide pliability. "A 43% high-maltose corn syrup helps to produce a clear, hard candy piece since it is low in dextrose, while a high-dextrose syrup is a highly fermentable substrate for fermentation products," says Walbert. For applications requiring a dry ingredient, corn-syrup solids are available with various particle sizes and bulk densities. "Many formulations benefit from a blend of corn sweeteners," she adds, "with HFCS contributing sweetness and other functionalities, and corn syrup adding body and viscosity."

Not-so-simple sugars That simple word "sugar" encompasses a wide array of monosaccharides, disaccharides and higher-unit chains, each with its own sweetness and functional properties.

The sweetest of all naturally occurring sugars, fructose, is found in fruits, vegetables and honey. This monosaccharide is a reducing sugar, capable of combining with amino acids to produce desirable "brown" flavors and colors in products like baked goods. It also enhances flavor, especially fruit and chocolate profiles. "Fructose has a perceived sweetness of about 1.2 times sucrose," says Lori Napier, manager, technical services, Tate & Lyle. "Unlike HFCS, which includes dextrose and other sugars besides fructose, our Krystar® crystalline fructose contains a minimum of 99.5% fructose. This allows processors to take full advantage of fructose's functionalities. For example, when used with starches, such as in instant puddings, fructose will decrease set times and maintain viscosity with lower starch levels. Due to its unique sweetness profile, the sugar works synergistically with other carbohydrate and high-intensity sweeteners, enabling a reduction in sweetener levels and calories without decreasing sweetness perception. It is also an extremely good humectant and helps maintain pliability in cereal-type bars."

Dextrose, a reducing monosaccharide with about 67% of the sweetness of sucrose "supplies many of sugar's functionalities, without all of its sweetness," says Napier. "This makes it useful in applications that require a lower sweetness level. Dextrose provides a pleasant, mouth-cooling effect in products like powdered donuts, and is often used in baked goods for browning and in processed meats, like sausages, for a subtle sweetness and brown color."

Lactose, a disaccharide derived from milk, is a reducing sugar that is about one-sixth as sweet as sucrose. Useful as a flow agent, humectant and for crystallization control, lactose has application, for example, in baked products for browning, flavor and tender structure.

Trehalose, a nonreducing disaccharide, has a sweetness similar to sucrose. "Since Ascend(TM) trehalose is nonbrowning, it does not change the color of a product, plus its mild sweetness can enhance the flavor and modulate certain off-notes, such as bitterness," states Jim Kappas, director of international and emerging products, Cargill Health & Food Technologies, Minneapolis. "Reports indicate that this sugar is highly effective at stabilizing proteins against damage from desiccation or freezing." In ice cream and other frozen foods, trehalose can mimic sugar's ability to depress the freezing point, while beverages acquire enhanced mouthfeel. Also, its high glass-transition temperature helps inhibit crystallization in glassy confections and improves stability and resistance to recrystallization in icings and frostings.

Polyol particulars Polyols, or sugar alcohols, are sugar-free sweeteners produced by hydrogenating simple sugars or corn syrups. Product designers typically include polyols at the same level as sucrose. Sugar alcohols differ from sugar in that they provide fewer calories and are absorbed more slowly by the body, resulting in reduced glycemic and insulin responses. Often used in sugar-free and no-sugar-added products, polyols are noncariogenic.

"Each polyol is different in its functionality," says Peter Jamieson, research scientist, SPI Polyols, New Castle, DE. "For example, sorbitol is very soluble, while mannitol is not. This diversity allows polyols to be used across the spectrum of food systems. One property that all polyols share is their nonreactivity -- that is, they do not brown or create off-flavors when exposed to elevated temperatures or sensitive ingredients. Consequently, polyols can extend shelf life by maintaining product integrity and stability." Capable of holding water, these ingredients function as humectants and freeze-point depressants -- often in sugar-free products to provide "bulk" or viscosity.

Sorbitol, a monosaccharide with 0.6 times the sweetness of sucrose, functions as a humectant, shelf-life extender and sweetener in sugar-free baked goods; inhibits crystallization and enhances the texture of frozen foods; and reduces caramelization and stabilizes color in sausage.

Lactitol, a disaccharide derived from milk sugar, has a relative sweetness of 0.3 to 0.4 times that of sucrose and a low glycemic index (GI). "This polyol is closest in functionality to sucrose and can be used to replace sugar and even decrease sweetness in oversweetened products, while maintaining other product attributes," says Donna Brooks, product manager, Danisco Sweeteners, Ardsley, NY. "For example, lactitol yields sugar-free and reduced-sugar baked items with good crispness, like cookies, and no-sugar-added ice cream with texture and scooping characteristics comparable to standard products."

Xylitol is as sweet as sucrose and is typically used in sugar-free confections and gums. It enhances flavor and provides a pleasant cooling effect that improves mint flavor and heightens the freshness of berry profiles. Not only is xylitol noncariogenic, research has shown that it might also exhibit cariostatic qualities.

"Polyols that are not as sweet as sucrose are often used with high-intensity sweeteners to adjust sweetness," says Brooks. "Some processors would like to take advantage of the health and functional benefits of polyols without using non-nutritive sweeteners, and we are currently working on formulas that meet those requirements, such as brownies made with xylitol and no intense sweeteners."

Fruitful formulating Fruit-juice concentrates lend consumer appeal by appearing on the ingredient statement as "real fruit juice." High in monosaccharides, particularly fructose, juice concentrates like apple and pear are generally 70?Brix, while strawberry and blueberry are typically about 65?Brix. "Apple and pear concentrates have a neutral taste and serve to enhance the sweet character of a flavor, while concentrates from berries and soft fruits like peaches and apricots can add color and flavor along with sweetness," says Scott Summers, director, technical and quality services, Tree Top, Inc., Selah, WA.

Functionally similar to HFCS, juice concentrates can partially or fully replace other carbohydrate sweeteners in applications like beverages, nutritional-bar fillings, fruit candies and confections, salad dressings, ice cream and juice bars, jams and jellies, syrups, sauces, and glazes. "Juice concentrates are good humectants, which can improve the texture and extend the shelf life of items like cereal bars and baked goods," adds Summers. "They also work well in sweet cereal coatings, and can give these products a good point of difference."

A honey of a sweetener Composed primarily of glucose and fructose, honey is typically 1 to 1.5 times sweeter than sugar (dry-weight basis). It can hold moisture to extend shelf life, promotes color and flavor development, and has microwave reactivity (to act as a browning agent or surface coating in microwaveable products). About 95% of the carbohydrates in honey are fermentable, an advantage in bakery applications.

Honey has beneficial effects on the four basic tastes, as determined in a University of Georgia, Athens study funded by the National Honey Board, Longmont, CO. Honey enhanced sweetness intensity, particularly in products with low sweetness levels. It also improved acceptability of sour products like yogurt, citrus beverages and some bakery fillings. Honey also decreased bitterness perception, which can improve savory profiles and products with caffeine and other bitter substances. Additionally, honey reduced saltiness intensity, a benefit in salt-cured products like bacon and other savory foods.

Liquid honey is available in a variety of flavors, colors and viscosities to meet processing requirements. Dried honey ingredients, which often include other sweeteners and flow aids, are useful in seasonings and dry mixes or coatings.

Sweet on fiber Soluble dietary fibers like inulin, oligofructose and fructooligosaccharides (FOS) supply some of the sweetness of sucrose, while their water-holding capacities provide sugarlike textures. They can help mask the unpleasant notes and aftertastes often associated with ingredients like soy, whey and high-intensity sweeteners. These ingredients share some similarities, but are not all alike.

"There is no formal regulation to discriminate FOS and inulin. Inulin and FOS are both fructans, which are linear nondigestible fructose polymers linked by beta-2,1 glycosidic bonds, and mostly with a single glucose molecule at the end," explains Connie Lin, applications manager, Sensus America LLC, Monmouth Junction, NJ. "Inulin is usually extracted from chicory roots, which has a degree of polymerization (DP) ranging from 2 to 60. Most people use DP 10 as the cutoff; all fructans below DP 10 are FOS. Short-chain FOS are especially referred to short-chain fructans, DP 2 to 5, which are enzymatically synthesized from sucrose. Therefore, all FOS are inulins -- but not all inulins are FOS."

For sugar replacement, inulin can work as a bulking agent and functional ingredient, as well as supply some sweetness. "The sweetness of a native inulin powder -- extracted from chicory roots -- is about 10% sweetness versus sucrose, says Lin. "Enzymatically hydrolyzed liquid inulins, consisting of short-chain inulin molecules, can have a significant sweetness, about 50% versus sucrose." High-intensity sweeteners (HIS) can easily make up the difference thanks to inulin's masking abilities. "Conventional inulin powder is commonly used in combination with HIS to replace sugar," she continues. "The HIS is used very little, ranging from 0.002% to 0.005% depending on application. Inulin has a good synergy with HIS, which helps to reduce the use level of the HIS."

Derived from the chicory plant, "Raftilose® ingredients contain up to 95% oligofructose, which consists of linear chains of fructose," says Hilary Hursh, food and nutrition scientist, Orafti Active Food Ingredients, Malvern, PA. "Oligofructose has been shown to stimulate the growth of beneficial bifidobacteria in the intestinal tract, and has been clinically proven to boost calcium absorption. Our products are clean-flavored, white powders that contribute to browning, and can be used much like sugar." Often used with high-intensity sweeteners and/or polyols, applications include nutrition bars, beverages, baked goods and sugar-free confections.

"NutraFlora® is derived from sucrose originating from sugar cane or sugar beet and consists of 95% glucose-terminated short-chain fructooligosaccharides (scFOS(TM))," states Linda Douglas, Ph.D., R.D., scientific affairs manager, GTC Nutrition, Golden, CO. "Our ingredient is a prebiotic fiber that improves digestive function and increases calcium absorption." This fiber balances the cooling effect of polyols, can partially replace sugar and fat, and does not cause Maillard-reaction browning. In beverages, it remains in solution without clouding or gelling, while bar-type products maintain a soft, chewy texture.

Other carb players Depending on the targeted market and desired end product attributes, other carbohydrate nutritive sweeteners can lead to distinctive formulations.

Invert sugar, a liquid, results from inverting sucrose to its glucose and fructose constituents. Sweeter than granulated sugar, invert enhances flavor, resists crystallization and is a better humectant than sucrose. Typical uses include icings and fruit fillings for smooth texture and moisture retention and dairy products for crystallization control.

Obtained from germinated barley, malt ingredients are about 50% as sweet as sucrose, with a pleasant, malt flavor that complements bagels, pretzels, artisan breads, nutrition bars and cereals. "In baked goods, malt functions as a food source for yeast, contributes to crust color development and is a good humectant," says Joe Hickenbottom, vice president sales and marketing, Malt Products Corporation, Saddle Brook, NJ. "One commonly used ingredient is malt syrup, which contains about 80% solids, has a viscosity similar to corn syrup and is available dark or light colored." Other forms include malt extracts and spray-dried versions.

Clear and brown rice syrups offer sweetness and viscosity similar to malt syrup. With its light-brown color and slight flavor, "brown rice syrup is primarily used in nutrition bars, often by processors that want natural-type ingredients on the label statement," notes Hickenbottom.

Molasses, made from cane sugar and with a sweetness similar to sucrose, supplies natural color and flavor notes that range from dark brown and robust to very light brown and mild. It contributes to mouthfeel, helps control water activity and is an effective humectant. Applications include cookies, dark breads, baked beans, sauces and condiments.

"Another interesting sweetener is agave syrup, which is an organic, non-GMO product that comes from the agave plant in Mexico," adds Hickenbottom. Primarily used in health foods, it consists mainly of fructose, is sweeter than invert and has a very low GI.

Choosing the best nutritive carbohydrate sweetener for a food or beverage is like going into a candy shop. The selection is extensive and it takes some deliberation, but with the right choice, the end result can prove sweetly satisfying.    

Freelance technical writer Elaine Knehr holds a B.S. in Food Technology and an M.S. in Business Administration. Her 10 years of experience covers a wide range of food products.

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